Magnetic tape devices that read and write data from and to a running magnetic tape while making the magnetic tape accommodated within a cartridge run are presented.
The magnetic tape devices cannot properly read and write data in some cases due to speed fluctuations caused by a change in a frictional state between a head and a tape due to a smudge or an abrasion of the head, or a degradation of the tape. To address such a problem, for example, the following techniques are present.
A first technique is a technique for avoiding an access to a degraded area even if the degraded area is present on a magnetic tape and for enabling an access only to an area other than the degraded area in a method for managing a degraded area of a magnetic tape (for example, Patent Document 1). With the first technique, the magnetic tape is configured as a set of partitions, each of which is configured with a management block, and a plurality of data blocks succeeding the management block.
A magnetic tape device control unit skips a partition when information indicating that an access to a partition is prohibited is recorded in a management information block present at the beginning of the partition when data is recorded to a magnetic tape. Then, the magnetic tape device control unit records the data to a data block succeeding a management information block of a subsequent partition. Next, the magnetic tape device control unit skips a partition and reproduces data in a data block succeeding a management information block of a subsequent partition, if the information indicating that an access to the partition is prohibited is recorded in a management information block present at the beginning of the partition when data is reproduced from the magnetic tape.
A second technique is a technique for detecting an abnormality of a running speed of a magnetic tape in a data recorder (for example, Patent Document 2). With the second technique, a recording head and a reproducing head are arranged at specified intervals in a running direction of a magnetic tape. Data recorded by the recording head is reproduced by the reproducing head, and fed to an error detection circuit. The error detection circuit makes a comparison between a reference time, which is calculated on the basis of the specified interval and an appropriate speed, and a data reproducing time, feeds an error signal to a driving circuit when the error detection circuit determines that the speed of the magnetic tape mismatches the appropriate speed, and stops the magnetic tape.
Patent Document 1: Japanese Laid-open Patent Publication No. 11-242802
Patent Document 2: Japanese Laid-open Patent Publication No. 2002-298470